Abstract
Biofilms, which are complex microbial communities embedded in the protective extracellular polymeric substances (EPS), are difficult to remove in food production facilities. In this study, the use of acidic electrolyzed water (AEW) to remove foodborne pathogen biofilms was evaluated. We used a green fluorescent protein-tagged Escherichia coli for monitoring the efficiency of AEW for removing biofilms, where under the optimal treatment conditions, the fluorescent signal of cells in the biofilm disappeared rapidly and the population of biofilm cells was reduced by more than 67%. Additionally, AEW triggered EPS disruption, as indicated by the deformation of the carbohydrate C-O-C bond and deformation of the aromatic rings in the amino acids tyrosine and phenylalanine. These deformations were identified by EPS chemical analysis and Raman spectroscopic analysis. Scanning electron microscopy (SEM) images confirmed that the breakup and detachment of biofilm were enhanced after AEW treatment. Further, AEW also eradicated biofilms formed by both Gram-negative bacteria (Vibrio parahaemolyticus) and Gram-positive bacteria (Listeria monocytogenes) and was observed to inactivate the detached cells which are a potential source of secondary pollution. This study demonstrates that AEW could be a reliable foodborne pathogen biofilm disrupter and an eco-friendly alternative to sanitizers traditionally used in the food industry.
Highlights
Foodborne pathogens which persist in food processing facilities grow predominantly as biofilms rather than in planktonic mode (Barnes et al, 1999; Bae et al, 2012)
Pathogens encased in the extracellular polymeric substances (EPS)-rich matrix, provide a source of contamination when the biofilm interacts with food materials (Carpentier and Cerf, 1993)
Bacterial biofilm formation is a dynamic process with distinct phases of development (Hall-Stoodley et al, 2004)
Summary
Foodborne pathogens which persist in food processing facilities grow predominantly as biofilms rather than in planktonic mode (Barnes et al, 1999; Bae et al, 2012). Compared to planktonic cells, biofilm-associated cells are more resistant to external stresses such as antibiotics and detergents, they are extremely difficult to eliminate resulting in the onset of foodborne illness (Costerton et al, 1987; Hoiby et al, 2010). In the dynamic process, EPS facilitates the trapping of nutrients and maintenance of the structure integrity of the biofilm while providing a sanctuary for the encased bacterial cells (Li and Yu, 2011; Bassin et al, 2012). Pathogens encased in the EPS-rich matrix, provide a source of contamination when the biofilm interacts with food materials (Carpentier and Cerf, 1993). The structure of EPS reduces disinfectants access and possibly triggers bacterial tolerance to commonly used sanitizers (Flemming and Wingender, 2010; Xiao et al, 2012; Koo et al, 2013; Lebeaux et al, 2014)
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